类图

classDiagram
    class Course {
        +String courseID
        +String courseName
        +String description
        +addCourse()
        +updateCourse()
        +deleteCourse()
    }

    class ClassGroup {
        +String classID
        +String className
        +String grade
        +addClass()
        +updateClass()
        +deleteClass()
    }

    class AssignmentBank {
        +String assignmentID
        +String title
        +String content
        +selectAssignment()
        +listAssignments()
    }

    class Assignment {
        +String assignmentID
        +String courseID
        +Date deadline
        +assignToClass()
    }

    class Submission {
        +String submissionID
        +String studentID
        +String assignmentID
        +File file
        +Float grade
        +String feedback
        +reviewSubmission()
        +assignGrade()
        +addFeedback()
        +submitAssignment()
        +uploadFile()
    }

    class Authentication {
        +String userID
        +String role
        +verifyIdentity()
    }

    class Student {
        +viewAssignment()
        +downloadAssignment()
    }

    Course "1" --> "many" Assignment : manages
    Assignment "1" --> "many" Submission : assigned to
    AssignmentBank "1" --> "many" Assignment : contains
    ClassGroup "1" --> "many" Student : contains
    Student "1" --> "many" Submission : submits
    Submission --> Authentication : verify

关联，关联角色，关联数量关系

1	*	a..b